xxv.] CORN MILDEW AND BARBERRY BLIGHT. 179 



before his death, to say that he believed a large number of 

 his Swedish firwood fungi would be found in the firwoods 

 of Scotland if sought for ; but they are still but little 

 sought for, and therefore not in many instances found. 



There has long been an extremely common fungus in this 

 country named ^Scidium Tussilaginis, Pers., but till lately 

 its supposed alternate form, Puccinia Poarum, NieL, had not 

 been recorded, although the host plant of this fungus is 

 extremely common. Mr. Plowright in his experiments 

 (Grevillea, voL ii. p. 56) claims to have produced this 

 Puccinia artificially on Poa eleven days after infection from 

 the germinating dfieidiwn spores ; and on close search being 

 made, examples of Poa annua, L., were found growing natur- 

 ally and bearing the Puccinia. These facts as to the artificial 

 production and the ultimate discovery of the naturally- 

 grown Puccinia have been brought forward as evidence in 

 favour of the connection of ^Ecidium and Puccinia. We 

 are inclined to give but little weight to this part of the 

 evidence, for the j^Ecidium still remains extremely com- 

 mon and the Puccinia extremely rare, just as in the common 

 Uredo Rubigo-vera, D.C., and the excessively rare ^Ecidium 

 asperifolii, Pers., described in this work under Spring Rust. 



The believers in the connection of corn mildew and 

 barberry blight consider their views supported, and indeed 

 proved, by their experiments. The results of the experi- 

 ments leave no room they say for doubt ; still a great diffi- 

 culty rests with, all the experiments in regard to the lapse 

 of time which takes place between the application of the 

 infecting spores and the appearance of the fungus which is 

 supposed as a consequence to follow ; this period is some- 

 times more than twenty days. In the case of jEcidium 

 bellidis, D.C., as reported in the Journal of the Linnean 

 Society, vol. xx. p. 512, the time ranged from twenty- 

 four days to over two months. When a germ tube enters 

 the tissues of a plant through one of its organs of transpir- 

 ation, no one can follow it farther. Every microscopist 

 knows that a leaf is an opaque object, and no amount of 



